Machine translation (MT) concerns the automatic translation of natural language sentences from a first language (e.g., French) into another language (e.g., English). Systems that perform MT techniques are said to “decode” the source language into the target language.
A statistical MT system that translates French sentences into English has three components: a language model (LM) that assigns a probability P(e) to any English string; a translation model (TM) that assigns a probability P(f|e) to any pair of English and French strings; and a decoder. The decoder may take a previously unseen sentence f and try to maximize the e that find P(e|f), or equivalently maximizes P(e)·P(f|e).